Although a tremendous volume of research has addressed both physiological and sociocultural factors in substance abuse, surprisingly little research effort has been devoted to the role and importance of cognitive factors in this behavior. There is an important gap in the literature, especially in view of the fact that there is an established link between substance abuse and attention deficit hyperactive disorder (ADHD), a condition which results in a number of important cognitive anomalies. The proposed research will address the relationships between attention deficit disorder, related co-morbid conditions, and substance abuse behavior, with special reference to two types of cognitive processing which are likely to characterize the individual with ADHD, specifically metonymic processing and an enhanced vulnerability to the consequences of the availability heuristic in deciding whether or not to engage in substance abuse. A series of experiments is proposed which will characterize these relationships in a large non-referred adolescent population and in the general population of a culturally rich multi-ethnic area; this is especially important in that much of the available research on ADHD and substance abuse has addressed only referred populations, a source of significant potential bias. The proposed research is intended to result in a formal structural equation model of the relationships of ADHD, co-morbid conditions, cognitive processing factors, and substance abuse, from with a precise and predictive understanding of these relationships can be formed.